The present invention relates to an endoscope apparatus capable of obtaining a smooth diagnostic image suitable for observation at a high frame rate at the time of screening diagnosis and obtaining a high-definition diagnostic image at the time of detailed diagnosis by switching and using a plurality of kinds of illumination depending on purposes, such as screening diagnosis (observation) and detailed diagnosis (observation).
In diagnostic imaging using an endoscope, screening observation/inspection or screening diagnosis is performed in which cancer of a body cavity, particularly, the focus site of early-stage cancer, a lesion site, or an abnormal site, such as a hemorrhage, is observed accurately, precisely, and in detail, and prior to detailed observation for diagnosis or detailed diagnosis, a site suspected of abnormality is found from each site in a wide range of the body cavity.
In screening observation/diagnosis using the endoscope, it is necessary to observe and diagnose a wide range of the body cavity. For this reason, as observation/diagnostic images, it is necessary to observe and diagnose the wide range from a distance while moving inside the body cavity, and there is demand for bright images or smooth video (motion images).
In detailed observation/diagnosis by an endoscope, when the site suspected of abnormality found in the screening observation/diagnosis is approached, it is necessary to accurately diagnose whether or not the relevant site is an abnormal site, such as cancer. For this reason, with regard to observation/diagnostic images, it is necessary to observe and diagnose the relevant site being substantially fixed in a close contact or enlarged state, or to perceive biological changes in a plurality of features of the relevant site, and there is demand for obtaining a plurality of images using light having various wavelengths.
For this reason, screening observation/diagnosis (hereinafter, collectively called diagnosis) is generally performed by normal light observation by normal white illumination light, and detailed diagnosis is generally performed by special light observation of an enlarged target site. As special light observation, the following observation is performed: narrowband light observation in which light (narrowband light) in a narrow wavelength band having a specific center wavelength is irradiated onto the mucosal tissue of the biological object using the fact that the invasion depth of light in the depth direction with respect to a biological tissue depends on the wavelength of light, and tissue information at a desired depth of a biological tissue, particularly, information on the form of a blood vessel at a predetermined depth (surface layer blood vessel (blue: B), intermediate layer blood vessel (green: G), deep layer blood vessel (red: R), or the like) are obtained to determine the presence/absence of a focus, such as a cancer tissue; narrowband light observation in which narrowband light in the B region is irradiated onto a biological tissue using the absorbance of hemoglobin and the oxygen saturation in blood is measured; infrared light observation in which near-infrared light is irradiated onto a biological tissue using the absorbance of hemoglobin or the absorbance of ICG (indocyanine green) to be bound to protein and the oxygen saturation in blood is measured to image a blood vessel; or fluorescent observation in which the presence/absence of a focus, such as cancer cells, is diagnosed using autogenous fluorescence generated from a biological tissue, onto which excitation light in a specific narrow wavelength band is irradiated or fluorescence generated from a fluorescent medication dispersed in a specific focus, such as cancer cells, in a biological tissue.
Patent Document 1 describes an endoscope apparatus for enlarged observation in which the magnification of a subject image is variable by a remote operation. In this endoscope apparatus, an objective lens optical system which can perform normal observation and a confocal optical system which can obtain an enlarged microscopic image of a subject are provided together at the tip of an insertion portion. A video processor and a main monitor for the objective lens optical system, and a confocal image processor and a confocal image monitor for the confocal optical system are separately provided.
In the endoscope apparatus for enlarged observation described in Patent Document 1, normal white illumination light which is emitted from a light source lamp in the video processor and enters the objective lens optical system is irradiated toward a subject, reflected light from the subject is received by a solid-state imaging element to perform imaging, a captured image signal is processed by a video signal processing circuit in the video processor, and a captured subject image is displayed on the main monitor. In this way, screening by normal observation is performed. In this screening, if a site suspected of abnormality is found, the remote operation of the objective lens optical system is performed to enlarge the magnification of the subject image of the relevant site to the enlargement magnification of the confocal optical system, and the enlarged image is displayed on the main monitor. Thereafter, in the confocal optical system, reflected light by laser light which is emitted from a laser light source in the confocal image processor and enters the confocal optical system is received by a light-receiving element in the confocal image processor, the video signal is processed by a video signal processing circuit, and the enlarged microscopic image of the subject is displayed on the confocal monitor.
In this way, in the endoscope apparatus for enlarged observation, it is possible to perform detailed diagnosis on a enlarged microscopic image corresponding to the enlarged image of the site suspected of abnormality found in screening.
With regard to special light observation, Patent Document 2 describes an endoscope system which has three observation modes including a normal light observation mode in which a reflected light image is presented, a screening fluorescent observation mode (first fluorescent observation mode) in which a fluorescence intensity image is presented, and an unmixing fluorescent observation mode (second fluorescent observation mode) in which the concentration distribution of a fluorescent medication obtained by computation from a fluorescence intensity image is presented, and can select an appropriate observation mode by a mode selector.
In this endoscope system, a white light source, such as a xenon lamp, a light source for illumination light constituted by a switching RGB color filter, and two excitation light sources constituted by semiconductor lasers which emit excitation light having different wavelengths with the peak wavelengths of 680 nm and 700 nm are used as light sources. While the insertion portion at the tip of the endoscope is inserted into a body cavity and then reaches an observation site, imaging is done in the normal light observation mode using the light source for illumination light, that is, normal screening is performed. In the normal light observation mode, a light source for illumination light is constantly turned on, reflected light by RGB frame sequential light by RGB color filters is received by the imaging element to image the observation site as a color image, and the color image of the observation site is displayed on a display unit. In this mode, the two excitation light sources are turned off. If the insertion portion at the tip of the endoscope reaches the observation site, the observation mode is switched to the screening fluorescent observation mode, such that the observation-target site is cleaned and two fluorescent probes are dispersed.
In the screening fluorescent observation mode, the light source for illumination light and one excitation light source are used, and another excitation light source is not used. When the light source for illumination light is turned on, only B illumination light is irradiated onto the observation site by the color filters and imaged by the imaging element as a reflected image (B). When one excitation light source is turned on, two kinds of fluorescence which are generated when two fluorescent probes dispersed in the observation target are excited by emitted excitation light are imaged by the imaging element including an excitation light cut filter as a fluorescent image, and are displayed on the display unit as an image in which the fluorescent image and the reflected light image overlap each other. If fluorescent is not generated, the observation mode is switched to the normal observation mode, and the insertion portion at the tip of the endoscope moves to the next observation site. If fluorescent is not generated, the observation mode is switched to the unmixing observation mode.
In the unmixing observation mode, the light source for illumination light and the two excitation light sources are used. In the same manner as described above, two kinds of fluorescent images in which a reflected light image and two kinds of fluorescence are color-mixed are acquired, concentration information of the fluorescent probes is calculated from the two kinds of fluorescent images, and displayed on the display unit to overlap the reflected light image. It is possible to diagnose the presence/absence of a cancer cell on the basis of the concentration information by the two kinds of fluorescence.
[Patent Document 1] JP 2008-22890 A
[Patent Document 2] JP 2008-161550 A